At present, radio communication systems such as mobile phone systems and wireless LANs (Local Area Networks) are widely used. Many radio communication apparatuses each include a radio unit (RF unit) that performs radio signal processing, and a baseband processing unit (BB unit) that performs baseband signal processing. The radio unit and the baseband processing unit each may be made into chips as an RFIC (Integrated Circuit) and a BBIC, and both may be used by being connected by a signal line.
Here, the RFIC and the BBIC may be connected by a digital signal line. There is DigRF as a digital interface standard between the RFIC and the BBIC. DigRF specifications are discussed in a working group in the MIPI (Mobile Industry Processor Interface) Alliance. According to the DigRF, a BBIC packetizes I/Q (In-phase/Quadrature) data to transmit and control data used for control of an RFIC, and transmits the packetized data to the RFIC. Furthermore, the RFIC packetizes the received I/Q data, and transmits the packetized data to the BBIC.
Note that, with respect to the DigRF, a radio communication apparatus is proposed in which a BBIC preliminarily transmits, to an RFIC, transmission information indicating timing schedule for a transmission burst, and the RFIC controls the transmission of the transmission burst autonomously (for example, see, International Publication Pamphlet No. WO2006/102922). Furthermore, a radio communication apparatus is proposed in which a plurality of setting patterns is preliminarily stored inside an RF transceiver, and the RF transceiver selects a corresponding setting pattern and applies the setting pattern to a sub-circuit when a baseband device requests a specific operation mode from an RF device (for example, see, paragraphs [0024] and [0025] in Japanese Laid-open Patent Publication No. 2009-105881).
Meanwhile, it is contemplated that a radio unit and a baseband processing unit, when transmitting and receiving control data in a packet format, performs retransmission control. That is, it is contemplated that the radio unit performs the error detection on the control data of the packet format received from the baseband processing unit, requests retransmission from the baseband processing unit when an error is found, and performs processing based on the control data when an error is not found. However, when retransmission control is performed on control data, a delay accompanying retransmission may become a problem, depending on a content of processing performed by the radio unit.
For example, there may also be a case where when the radio communication apparatus obtains control information (for example, information on transmission power control) on radio communication from another radio communication apparatus of a communication partner, it is required that the radio communication apparatus performs, within a predetermined time from obtaining the control information, processing (for example, change in transmission power of the radio unit) in accordance with the control information. However, when the baseband processing unit generates control data after obtaining the control information and transmits the control data to the radio unit, and the retransmission of the control data occurs, there is also a possibility that the radio unit is not able to perform the processing within the predetermined time from obtaining the control information.